I have a case 590 super M that had a f/r problem. On selecting f or r on the shuttle, it would want to move but didn't. A member Silverman suggested I check the shuttle relay and I die electric greased the connection and it worked. Now, when I select a drive, there's a voltage drop on the volt meter then I can hear a whirring or vibrating sound, hard to pin point with the engine making so much noise. I crawled underneath, but I don't see any electrical connection on the trans but have some on the rear end. I figured the rear end selects the f/r, but what do I really check to see what's faulty?
To highway ghost, you helped me with the no drive before which came out to be a bad connection on the shuttle relay. I checked it again, but no luck, so I bought a new relay, $167 later but still no drive. After selection f or r, I can hear a buzzing sound below the floorboard. On the rear end, I see where there is one hydraulic line that is connected to the shifting fork that I presume selects f or r. I'm going to try and locate the source of the hydraulic hose and see if there's a solenoid that selects the hydraulic pressure in or out. Any other ideas?